RESUMO
Geophysical surveys have been widely used for geological mapping, and with appropriate ground calibration the database can be converted to radiometric surveys. Herein we present a case study of a high resolution map of the City of Rio de Janeiro, Brazil, constructed by integrating aerial and in situ (ground) measurements. This allowed assessing the influence of urbanization observed between 1978 and 2009 on radiation external exposure. Radiometric, geological and demographics databases were integrated in a Geographic Information System (GIS) facility. The average absorbed dose rate recorded for the city was 96 ± 0.3 nGy h(-1) and ranged from 22 to 152 nGy h(-1) among districts. The corresponding annual effective dose was determined as 0.09 ± 0.01 mSv. The number of people at risk per year according to the estimated natural radiation levels was 17 ± 1.4, among the 28,000 new cases estimated by the INCA (Brazilian National Cancer Institute) within a population of approximately 6.3 million people.
Assuntos
Monitoramento de Radiação , Brasil , Sistemas de Informação Geográfica , Medição de Risco , UrbanizaçãoRESUMO
In order to study the process of dispersion and the activity concentration of 232Th and 238U series and 40K radionuclides in two island beaches in southeastern Brazil, analyses was made of sand samples of 0-10 cm profile, during a 12-month period. Moreover, the monthly variations of gamma dose rates were studied to determine the local environment absorbed dose rate. The average activity concentration of primordial radionuclides 232Th, 238U and 40K at Preta beach, they were 239, 121 and 110 Bq kg(-1), while at Dois Rios beach they were 48, 39 and 412 Bq kg(-1), respectively. The absorbed dose rate in air, observed at 1 m above the ground, ranged from 54 to 228 nGy h(-1) at Preta beach and from 39 to 110 nGy h(-1) at Dois Rios beach. The annual effective dose equivalent corresponding to Preta beach is 0.15 mSv a(-1) and to Dois Rios 0.08 mSv a(-1).